jit | 易学教程

How to see JIT-Compilated code in .NET VM (CLR)

阅读更多关于 How to see JIT-Compilated code in .NET VM (CLR)

问题 How can I have a trace of native code generated by the JIT-Compiler ? Thanks 回答1: In Visual Studio place a breakpoint in the code and start debugging. When it breaks, open the Disassembly window (Debug > Windows > Disassembly or Alt+Ctrl+D). 回答2: If you just use Debug->Windows->Disassembly on a standard Debug or Release exe, without modifying Visual Studio Debugging options, you will just see a version of non optimized .NET code. Have a look at this article "How to see the Assembly code

Will the jit optimize new objects

阅读更多关于 Will the jit optimize new objects

问题 I created this class for being immutable and having a fluent API: public final class Message { public final String email; public final String escalationEmail; public final String assignee; public final String conversationId; public final String subject; public final String userId; public Message(String email, String escalationEmail, String assignee, String conversationId, String subject, String userId) { this.email = email; this.escalationEmail = escalationEmail; this.assignee = assignee;

Retrieve JIT output

阅读更多关于 Retrieve JIT output

问题 I'm interested in viewing the actual x86 assembly output by a C# program (not the CLR bytecode instructions). Is there a good way to do this? 回答1: You should use WinDbg with SOS/SOSEX, ensure that method you want to see x86 code for is JITted in method tables and then see actual unassembly with u command. Thus you would see actual code. As others mentioned here, with ngen you could see code that is not exactly matches actual JIT compilation result. With Visual Studio it is also possible

Do any JVM's JIT compilers generate code that uses vectorized floating point instructions?

阅读更多关于 Do any JVM's JIT compilers generate code that uses vectorized floating point instructions?

Let's say the bottleneck of my Java program really is some tight loops to compute a bunch of vector dot products. Yes I've profiled, yes it's the bottleneck, yes it's significant, yes that's just how the algorithm is, yes I've run Proguard to optimize the byte code, etc. The work is, essentially, dot products. As in, I have two float[50] and I need to compute the sum of pairwise products. I know processor instruction sets exist to perform these kind of operations quickly and in bulk, like SSE or MMX. Yes I can probably access these by writing some native code in JNI. The JNI call turns out to

C# JIT compiling and .NET

阅读更多关于 C# JIT compiling and .NET

I've become a bit confused about the details of how the JIT compiler works. I know that C# compiles down to IL. The first time it is run it is JIT'd. Does this involve it getting translated into native code? Is the .NET runtime (as a Virtual Machine?) interact with the JIT'd code? I know this is naive, but I've really confused myself. My impression has always been that the assemblies are not interpreted by the .NET Runtime but I don't understand the details of the interaction. Yes, JIT'ing IL code involves translating the IL into native machine instructions. Yes, the .NET runtime interacts

Why shouldn't I use PyPy over CPython if PyPy is 6.3 times faster?

阅读更多关于 Why shouldn't I use PyPy over CPython if PyPy is 6.3 times faster?

问题 I've been hearing a lot about the PyPy project. They claim it is 6.3 times faster than the CPython interpreter on their site. Whenever we talk about dynamic languages like Python, speed is one of the top issues. To solve this, they say PyPy is 6.3 times faster. The second issue is parallelism, the infamous Global Interpreter Lock (GIL). For this, PyPy says it can give GIL-less Python. If PyPy can solve these great challenges, what are its weaknesses that are preventing wider adoption? That is

Do modern JavaScript JITers need array-length caching in loops?

阅读更多关于 Do modern JavaScript JITers need array-length caching in loops?

问题 I find the practice of caching an array's length property inside a for loop quite distasteful. As in, for (var i = 0, l = myArray.length; i < l; ++i) { // ... } In my eyes at least, this hurts readability a lot compared with the straightforward for (var i = 0; i < myArray.length; ++i) { // ... } (not to mention that it leaks another variable into the surrounding function due to the nature of lexical scope and hoisting.) I'd like to be able to tell anyone who does this "don't bother; modern JS

How to alloc a executable memory buffer?

阅读更多关于 How to alloc a executable memory buffer?

问题 I would like to alloc a buffer that I can execute on Win32 but I have an exception in visual studio cuz the malloc function returns a non executable memory zone. I read that there a NX flag to disable... My goal is convert a bytecode to asm x86 on fly with keep in mind performance. Does somemone can help me? JS 回答1: You don't use malloc for that. Why would you anyway, in a C++ program? You also don't use new for executable memory, however. There's the Windows-specific VirtualAlloc function to

What is microbenchmarking?

阅读更多关于 What is microbenchmarking?

I've heard this term used, but I'm not entirely sure what it means, so: What DOES it mean and what DOESN'T it mean? What are some examples of what IS and ISN'T microbenchmarking? What are the dangers of microbenchmarking and how do you avoid it? (or is it a good thing?) In silico It means exactly what it says on the tin can - it's measuring the performance of something "small", like a system call to the kernel of an operating system. The danger is that people may use whatever results they obtain from microbenchmarking to dictate optimizations. And as we all know: We should forget about small

Does the .NET CLR JIT compile every method, every time?

阅读更多关于 Does the .NET CLR JIT compile every method, every time?

问题 I know that Java\'s HotSpot JIT will sometimes skip JIT compiling a method if it expects the overhead of compilation to be lower than the overhead of running the method in interpreted mode. Does the .NET CLR work based upon a similar heuristic? 回答1: Note: this answer is on a "per-run" context. The code is normally JITted each time you run the program. Using ngen or .NET Native changes that story, too... Unlike HotSpot, the CLR JIT always compiles exactly once per run. It never interprets, and